Is this tub vented properly?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by riverguy, Nov 23, 2012.

  1. riverguy

    riverguy New Member

    Messages:
    3
    Location:
    Texas
    Hey all I am looking for some help on my tub venting. The house is 40 years old. The picture attached is what the plumbing looks like. I have had the toilet off and run water through so I know the sink and the tub both connect under the toilet and then go to the septic.

    Both the sink and the toilet are fine and I think they are adequately vented based that the roof vent is on the same wall with them. The tub doesn't have a vent and its pipe goes across the bathroom floor then ties into the toilet.

    When you shower, there is an inch or so of water in the shower and the tub gurgles through the overflow vent. I have made sure no hair, etc is clogged on the X part of the drain. Would adding an air admittance valve on the pipe where the tub overflow connects to the drain give me more venting for better draining?

    Thanks a lot

    Attached Files:

  2. mikeplummer

    mikeplummer Plumber

    Messages:
    190
    Location:
    Ontario, Canada
    from your image and description - it is not vented properly
    adding an AAV where you suggest will do nothing as the overflow is exposed to atmosphere anyways.
    the slow draining is most likely due to partial blockage or possibly improperly sloped piping.
  3. riverguy

    riverguy New Member

    Messages:
    3
    Location:
    Texas
    I thought of adding the AAV there because I wasn't sure if the overflow was enough venting. When I put the tub in two years ago I snaked the line. The tub has a push in drain cover with multiple small holes in it and that usually catches any hair so I'm not sure if it is clogged. Can't be sure though. Also, as far as I can remember, the tub does not make a tornado when it drains.
  4. mikeplummer

    mikeplummer Plumber

    Messages:
    190
    Location:
    Ontario, Canada
    the overflow is does not serve as a vent. the venting is to protect the trap from siphonage and would be located downstream of the trap.
    i am glad to hear you arenèt creating tornadoes.... drainage would be the least of your worries in that case :p
  5. riverguy

    riverguy New Member

    Messages:
    3
    Location:
    Texas
    So am I out of luck on venting this properly? The floor is tile/slab.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,782
    Location:
    Bothell, Washington
    The overflow is open to the tub, acting as an "overflow". If the water gets too high, the water goes down the overflow. It's already considered an open pipe. Making it more open doesn't change anything.
    If there is standing water in the tub, then snaking is the answer.
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,237
    Location:
    Land of Cheese
    More often than not, a tub is best snaked by removing the cover from the overflow and snaking through it. This allows you to fully snake through the trap and beyond, which cannot often be done through the tub shoe.
  8. wjcandee

    wjcandee Wise One

    Messages:
    1,770
    Location:
    New York, NY
    Maybe this would be helpful:

    I think like a lot of smart people, you haven't quite been properly-informed about the purpose of proper venting and the effects of improper venting.

    The gang is telling you the correct info (after all, look at the credentials of the gang advising you), but it may not be making complete sense given your understanding of venting.

    First things first: Even in a 100-percent-to-Code installation, it's "okay" to have the tub at "the end of the line". That is, in a properly-vented installation, you do not need a vent upstream of the tub, and, in any event, you're not going to have one upstream of the p-trap. You don't need it for the tub to drain properly. And, as everyone has pointed out, you already have a pipe open to the atmosphere "upstream" of your drain by dint of the overflow. So even 100% proper venting isn't going to affect the draining of your tub.

    Now, the question you asked is whether it is properly-vented, and the answer is probably "no". You say it ties into the toilet. Not sure exactly what you mean, but it certainly isn't unusual or improper to tie the drain line from the bathtub into the waste line of the toilet downstream of the toilet. Maybe that's what you installation does; I don't know. And if, at the point of the tie-in, the trap arm of the p-trap for the tub is vented, you'd be okay if that trap arm was 3.5 feet or less. (The trap arm on a 1.5 inch line should be no more than 3.5 feet.) Chances are the distance from the tub drain to toilet is more than 3.5 feet, and it's unclear how the whole thing is tied together, so you are probably not correctly vented.

    But what of that? And what's the effect? Here, the concern about properly-venting is to keep the toilet from siphoning the trap in the bathtub when you flush. Adding an AAV upstream of the tub trap or on the overflow isn't going to affect the siphoning, and likewise it's not going to do anything to help your tub drain.

    Does this make sense? Hope this helps.

    More likely, you've got an accumulation of gunk somewhere (or an improperly-sloped line), and that's the cause of your slow drainage. Snaking is probably your best bet.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,270
    Location:
    Cave Creek, Arizona
    IF the tub is "gurgling" while it is draining, it is draining AS FAST as possible so the obstruction is in the tub itself, not the overflow OR the drain. The gurgling sound is what I use to determine if the drain is plugged up, because if the water is not draining properly the pipe fills and the water does not aspirate air. The aspiration, or gurgling, is the fast moving water sucking air down the overflow pipe, which is what you want to happen. You probably have a drain cover which restricts the water flow, or your drain's "trip lever" is not lifting the plug high enough. A "bad" vent seldom prevents or slows drainage, unless there is another problem elsewhere. IF there is no problem the lack of a vent will usually cause FASTER drainage. The vent is only a factor at the end of the drainage cycle when the "faster" drainage would cause a problem with the trap seal.
    Last edited: Nov 24, 2012
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